Viability of nasoseptal flap in a previously radiated field

Abstract

Background: Nasoseptal flap is a pedicle mucosal flap based on the nasoseptal branch of the sphenopalatine artery. The flap is frequently used in reconstruction of the skull anterior skull base after endoscopic skull base surgery. Certain patients may be previously treated with high dose radiation with the pedicle of the flap in the high dose zone of radiation. The blood supply to the nasoseptal flap may then be jeopardized by the prior radiation. The current study investigates the viability of the nasoseptal flap harvested from a previously irradiated area. Materials and Methods: 25 patients with nasopharyngeal carcinoma (NPC) treated with radiation had nasoseptal flap harvested to cover the raw area of nasopharynx and clivus after surgery. 8 patients had open maxillary swing nasopharyngectomy for locally recurrent NPC and contralateral nasoseptal flaps were harvested to cover the raw area of the clivus. 4 NPC patients previously treated with radiation suffered from osteoradionecrosis of the nasopharynx who underwent endoscopic debridement and nasoseptal flap were harvested endoscopically to cover the raw area. 13 patients underwent robotic nasopharyngectomy and nasoseptal flaps were harvested endoscopically at the conclusion of the procedure. All patients had endoscopic debridement and assessment of the viability of the nasoseptal flap 4 weeks after the operation. The original images of the flap at the conclusion of the procedure were used as reference. The viability of the flap is classified into 4 grades. Grade 1, 0-25% of the flap viable; grade 2, 25- 50% of the flap viable; grade 3, 50-75% of the flap viable; grade 4, 75-100% of the flap viable. Results: All flaps were successfully harvested and inset to cover the raw area in the nasopharynx. 16 (64%) flaps had minimal loss of tissue (grade 4) and 5 (20%) patients and moderate amount of flap necrosis (grade 3) with the distal part of the flap not being viable. 4 (16%) patients had complete loss of flap (grade 1). Defining flap failure as any tissue loss >25% (grade 1-3), patients received more than one course of radiation did not have increased risk of flap failure (p=0.21, Fisher's exact test) and patients with radiation more than 5 years before the time of harvesting the flap (p=1.00, Fisher's exact test) Conclusion: For patients with prior radiation to the central skull base and nasopharynx area, the nasoseptal flap may not be totally reliable and partial or total flap loss can occur. Alternative reconstruction techniques should be considered in the primary reconstruction or salvage in case of failure of the nasoseptal flap.